Prices of single-family homes fell almost double the expected pace in October, the fourth straight decline, data from a closely watched survey showed on Tuesday, fresh evidence the housing market continues to struggle.

The Standard & Poor's/Case-Shiller composite index of 20 metropolitan areas declined 1.0 percent in October from September on a seasonally adjusted basis, faster than the 0.6 percent drop expected by economists polled by Reuters.

The drop followed a seasonally adjusted decline of 1.0 percent in September.

S&P, which publishes the indexes, also said home prices in the 20 cities index fell 0.8 percent from October 2009.

Unadjusted for seasonal impact, the 20-city index fell 1.3 percent in October after a 0.8 percent decline in September.

(Reporting by Corbett B. Daly; editing by Jeffrey Benkoe)